The present invention relates generally to turnbuckle assemblies for connecting tie rods and the like in motor vehicles, and in particular to a new and improved prevailing torque adjusting sleeve for such a turnbuckle.
Hexagonal turnbuckle sleeves having prevailing torque deformations in the turnbuckle sleeve caused by opposing dies deforming the turnbuckle sleeve is conventionally known in the art of vehicle steering controls. In the present invention, the stems of two tie rod ends are threaded into a turnbuckle sleeve in a conventional manner. The sleeve is cylindrical in shape, and may also have a hexagonal outer surface for facilitating adjustment with a wrench. After the stems are inserted to the desired depth, the turnbuckle sleeve is positioned between two opposed crimping dies. These dies are formed with a "V" notch portion on one face of each die, which notches oppose one another when the dies are operably disposed. Pressure is then applied, forcing the dies together, thereby deforming the turnbuckle sleeve into the threaded stems of the tie rods. Due to the shape of the dies, the turnbuckle sleeve will be deformed at equally spaced positions around the body of the sleeve and deformed throughout its entire length except at the ends. It is important that the turnbuckle sleeve is deformed only to the extent that a controlled turning torque results from the crimping pressure. This is the torque considered sufficient to maintain tightness under operating loads and vibration while permitting subsequent adjustment for the standand wrench. It should also be noted that in the case of a cylindrical outside surface for the turnbuckle, the deformation will provide for the necessary flat surfaces for subsequent adjustment with a standand wrench.
It is one object of the present invention to hold the threaded parts together in a positive yet adjustable fashion and with light deformations over the entire area of the sleeve such that the deformations are spread out instead of being concentrated. Concentrated deformations pose the problem that whenever the turnbuckle parts are relatively rotated, the concentrated deformed parts cause thread wear and hence limit the amount of adjustment that can be made over an extended period of time. By having the deformations spread out or distributed evenly, a significantly greater amount of adjustment can be accomplished a number of times without wearing out the threads.
The present invention also has an object to achieve substantially either two or four separately circumferentially spaced deformations in the sleeve. The four deformation contacts are preferable in order to create four lines of contact and provide a substantially circular cross-section for the threads on the interior of the sleeve. An oval shaped cross-section, with two contact lines of deformation, however, is also within the scope of the present invention.
It is a further object of the present invention to limit the amount of prevailing torque for adjustment of the sleeve to a controlled turning torque. In a typical automotive application, this prevailing torque is a total of 20 to 30 foot-pounds or 10 to 15 foot-pounds of torque at each end of the sleeve. In the present invention, the prevailing torque is controlled by the spacing between the deforming dies caused by the amount of space between the dies at which the machine stop is preprogrammed or otherwise set. By varying the spacing (changing the stop point), the total amount of prevailing torque may be limited as desired.
Another object of the present invention is to deform the sleeve over the major length of the sleeve. This deformation provides the advantages that no wiggle of the two tie rod ends will occur (i.e., they will be held solidly) and negligible change will occur in the prevailing torque feature after a number of readjustments (prior art sleeves have a localized interference fit area that wears away rapidly). Also, a short distance at each end is not deformed so that any subsequent replacement tie rod end may be easily started into the threads.
Other objects and advantages of the instant invention will be apparent in the following specifiation, claims and drawings.